The present invention relates a ferrule that is a part of a plug constituting an optical connector for optical connection, particularly to a collar member that constitutes the ferrule.
Optical connectors currently used in communication provide optical connection by inserting and fixing an optical fiber in a ferrule processed with high precision to have accurate inner diameter and outer diameter, polishing the optical fiber facet to be connected into a convex spherical shape, and physically contacting the optical fiber with another optical fiber.
The ferrule into which an optical fiber is inserted to be held is usually composed of a ferrule tubular body and a collar member. The ferrule tubular body is formed from hard ceramic such as zirconia or from glass, and has an optical fiber insertion hole. The collar member is formed at the rear end of the ferrule tubular body from a metal such as stainless steel, and has a hollow hole communicated with the rear end of the optical fiber insertion hole. An optical fiber, namely, a coated optical fiber with its tip removed of coating, is inserted in the optical fiber insertion hole formed inside the ferrule tubular body, and the inserted optical fiber is bonded to the ferrule with an adhesive or the like.
However, the collar member is formed by cutting a metal, and bite wear caused during the cutting results in fluctuation in inner diameter of the hollow hole to be fitted with the ferrule. tubular body. When the collar member whose hollow hole has fluctuating inner diameter is fitted to the rear end of the ferrule tubular body, the pressure applied to the ferrule tubular body also fluctuates to cause error. To form the entire collar member from a metal has another problem of high manufacturing cost.
The present invention has been made in view of the above, and an object of the present invention is therefore to provide a collar member and a ferrule with improved dimensional precision, simplified processing steps, and reduced cost.
A first aspect of the present invention to attain the above object is a collar member provided at the rear end of a ferrule tubular body that has an optical fiber insertion hole to which an optical fiber is inserted, characterized by comprising:
a metal pipe member with an inner diameter that allows the pipe member to accommodate the ferrule tubular body;
a collar portion integrally molded of plastic on the outer periphery of the pipe member, the collar portion having on its outer peripheral surface a key groove for positioning with respect to an optical connector housing;
a coated fiber holding portion integrally molded of plastic in the rear half of the pipe member to have an inner diameter smaller than the inner diameter of the pipe member, the coated fiber holding portion receiving therein a coated optical fiber that is obtained by coating the outer periphery of an optical fiber.
A second aspect of the present invention is a collar member of the first aspect of the invention, characterized in that the collar portion and the coated fiber holding portion are integrally formed in a one-piece construction.
A third aspect of the present invention is a collar member of the first or second aspect of the invention, characterized in that the collar portion and the coated fiber holding portion are engaged with the pipe member so that they are restricted in their axial and rotational movement.
A fourth aspect of the present invention is a collar member of the first aspect of the invention, characterized in that the pipe member has projections projecting therefrom toward the axial direction thereof on its outer peripheral surface in at least one location where the collar portion is formed, or on its inner peripheral surface where the coated fiber holding portion is formed, so as to engage the collar potion or the coated fiber holding portion to restrict axial and rotational movement thereof.
A fifth aspect of the present invention is a collar member of the first aspect of the invention, characterized in that the pipe member has on its outer peripheral surface a plurality of grooves formed along the circumference thereof, so as to engage the collar potion or the coated fiber holding portion to restrict axial and rotational movement thereof.
A sixth aspect of the present invention is a collar member of the first aspect of the invention, characterized in that the pipe member has on its outer peripheral surface a helical groove.
A seventh aspect of the present invention is a collar member of the first aspect of the invention, characterized in that the pipe member has an engagement hole opened on its outer peripheral surface, so as to engage the collar potion or the coated fiber holding portion to restrict axial and rotational movement thereof.
An eighth aspect of the present invention is a collar member of the first aspect of the invention, characterized by further comprising a planar portion on the collar portion side end of the pipe member spreading in the radial direction, the planar portion having an engagement hole to be engaged with the outer peripheral surface of the collar portion to restrict axial and rotational movement thereof.
A ninth aspect of the present invention is a collar member of the eighth aspect of the invention, characterized in that the engagement hole is tapered such that it becomes wider toward the front end of the pipe member.
A tenth aspect of the present invention is a collar member of the eighth aspect of the invention, characterized in that a plurality of the engagement holes are provided, the holes being arranged symmetrically with respect to the axis of the pipe member.
An eleventh aspect of the present invention is a collar member of the eighth aspect of the invention, characterized in that a projecting outer peripheral portion is formed in a part of the planar portion, the outer peripheral portion projecting radially from the outer peripheral surface of the coated fiber holding portion.
A twelfth aspect of the present invention is a collar member of the eleventh aspect of the invention, characterized in that the outer peripheral portion projects from the center of the planar portion toward the extension direction of the engagement hole.
A thirteenth aspect of the present invention is a collar member of the first aspect of the invention, characterized in that an end face to be engaged with the outer periphery of the coated fiber holding portion is formed in the rear half of the pipe member extending in the axial direction thereof.
A fourteenth aspect of the present invention is a collar member of the thirteenth aspect of the invention, characterized in that a hole is formed in the center of the end face.
A fifteenth aspect of the present invention is a collar member of the fourteenth aspect of the invention, characterized in that the hole is elliptical.
A sixteenth aspect of the present invention is a collar member of the fifteenth aspect of the invention, characterized in that the major axis of the elliptical hole coincides with the direction of the key groove.
A seventeenth aspect of the present invention is a collar member of the fourteenth aspect of the invention, characterized in that a pair of concave portions or a pair of convex portions are formed on the inner periphery of the hole such that the concave or convex portions are symmetrical with respect to the axis of the hole.
An eighteenth aspect of the present invention is a ferrule characterized by comprising:
a ferrule tubular body having an optical fiber insertion hole to which an optical fiber is inserted;
a pipe member with an inner diameter that allows the pipe member to fit with the ferrule tubular body;
a collar portion integrally molded on the outer periphery of the pipe member from plastic, the collar portion having on its outer peripheral surface a key groove for positioning with respect to an optical connector housing; and
a coated fiber holding portion integrally molded in the rear half of the pipe member from plastic to have an inner diameter smaller than the inner diameter of the pipe member, the coated fiber holding portion receiving therein a coated optical fiber that is obtained by coating the outer periphery of the optical fiber.
A nineteenth aspect of the present invention is a method of manufacturing a collar member, characterized by comprising the steps of:
forming through press molding a pipe member with an inner diameter that allows the pipe member to fit with a ferrule tubular body; and
forming through injection molding a collar portion and a coated fiber holding portion on the outer periphery of the pipe member and in the rear half of the pipe member, respectively, the collar portion having on its outer peripheral surface a key groove for positioning with respect to an optical connector housing, the coated fiber holding portion having an inner diameter smaller than the inner diameter of the pipe member, and the coated fiber holding portion receiving therein a coated optical fiber obtained by coating the outer periphery of the optical fiber.
According to the present invention specified as above, the collar member of the ferrule is composed of a pipe member and a collar portion and a coated fiber holding portion which are integrally molded from plastic so as to be integrated with the pipe member. Therefore the dimensional precision can be improved and the manufacturing cost can be reduced.